Stage Device Optical Axis Z-Motion Abbe Error Reduction
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Solution Overview
Problem
Existing stage devices for charged particle beam systems face increased costs and positioning errors due to the need for multiple interferometers and elevated mirror heights, which lead to increased movable mass and thermal deformation, affecting Abbe error and field-of-view positioning accuracy.
Innovation Solution
A stage device with a Z-axis mechanism that moves the optical axis of the laser interferometer, allowing for reduced mirror weight and Abbe error without increasing the stage's size or movable mass, by integrating the interferometer and mirror movement within the sample chamber, and using a penta-Dach mirror or prism to maintain optical axis alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the height of the mirror is increased to measure inclination in the Z direction, then the measurement capability is improved, but the movable mass of the stage increases and vibration increases
Solution Approach 1:
Instead of moving the mirror up and down with the stage, the patent inverts the approach by keeping the mirror stationary and moving the optical axis of the interferometer with the stage. This eliminates the need to increase mirror height while maintaining the ability to measure inclination in the Z direction across the full operating stroke.
Solution Approach 2:
The patent transitions from moving the mirror in the Z direction to moving the optical axis in the Z direction. This dimensional shift allows the same measurement function to be achieved without increasing the mirror's height or the stage's movable mass.
2Measurement precision
If the height of the mirror is increased to cover the Z direction operating stroke, then the measurement range is improved, but thermal deformation increases due to increased heat generation
Solution Approach 1:
The patent inverts the conventional approach by keeping the mirror stationary and moving the optical axis instead. This eliminates the need to increase mirror height to cover the Z direction operating stroke, thereby reducing heat generation and thermal deformation while maintaining full measurement range.
3Measurement precision
If multiple interferometers are added to measure inclination, then the measurement capability is improved, but the device complexity and cost increase
Solution Approach 1:
The patent makes the single interferometer multi-functional by enabling its optical axis to move in the Z direction. This allows the same interferometer to measure positions at different heights, eliminating the need for multiple interferometers while maintaining the capability to measure inclination and correct Abbe errors.
Solution Approach 2:
The patent introduces dynamic movement of the optical axis along the Z direction, transforming a static interferometer setup into a dynamic one. This allows a single interferometer to perform the function of multiple interferometers by adjusting its measurement plane to match the sample surface at different Z positions.
4Measurement precision
If the mirror height is increased, then the Abbe error reduction capability is improved, but the positioning error due to table deformation increases
Solution Approach 1:
The patent inverts the conventional approach by keeping the mirror stationary and moving the optical axis instead. This eliminates the need to increase mirror height, thereby avoiding the associated table deformation and positioning errors while maintaining the capability to correct Abbe errors through optical axis adjustment.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration reduces Abbe error and field-of-view positioning errors, improving accuracy and throughput while minimizing the stage's size and manufacturing costs by maintaining optical axis alignment and reducing thermal deformation.
Implementation Method 1
a laser interferometer that radiates a laser beam towards the mirror and receiving reflected light from the mirror to measure a position of the table in the X direction
Implementation Method 2
receiving reflected light from the mirror
Data Source
AI summary
The present invention is to provide a stage device capable of improving field-of-view positioning accuracy of a stage having a Z-axis mechanism. The invention is directed to a sample stage device having a first table that moves a sample in a first direction, a second driving mechanism that moves the first table in a second direction different from the first direction, and a part having a function of moving a laser interferometer optical axis that measures the position of the first table, in the second direction.